Constant tension drive



4 Sheets-Sheet l E. J'. CTTO CONSTANT TENSION DRIVE Filed May 8, 1 940Apri April '4, 1944. v E' J OTT@ 2,346,047

' CONSTANT TENSION DRIVE 1 Filed May 8, 1940 4 SheetsfSheet 2 April 4,1944. E, J. OTTO 2,346,047

CONSTANT TENSION DRIVE Filed May 8, 1940l 4 Sheets-Sheet 3 E-..lillllllllllllillll- ZI y 7 l 62,5/ ,5 .545/ 62 Ag, 4: 5111.135555 April4, 1944.' E;` 1 OTTO' CONSTANT TENSION DRIVE Filed May 8, 1940 4Sheets-Sheet 4 Patented Apr. 4, 1944 CONSTANT TENSION DRIVE I Eugene J.Otto, Milwaukee, Wis., assigner to Allisn Chalmers ManufacturingCompany, Milwaukee, Wis., a corporation o! Delaware i t Applicationvtray s, 1940, seran N'q. 333,891

scams. (c1. 'M -230.17)

This invention relates to a constant tension drive.'

In the treatment of continuous sheet, wire, etc., material, it is oftenof the utmost importance to maintain a constant tension on the strip ofmaterial' being wound or unwound, or in course of treatment. While manysystems are known for obtaining constant tension under such'circumstances, the present invention provides a drive of greatsimplicity and accuracy, and one which.

does not involve great expense. i

vIt is an object of thisinvention to provide a simple constant tensiondrive comprising a speed changer, thespeed ratio 'of which is' varied inresponse to changes in tension of the material being wound.` A furtherobject is to provide a drive of this type in which the speed changerratio is varied in response to a change in current consumption of thedriving motor. f 1

A further object of this invention is to provide, in a constant tension'drive, a speedchanger havin'g an output shaft driving amaterial-carrying roll and an inputshaft connected to a'source of power,and means responsive to a change in torque between the source of dpowerand saidinput shaft for varying the speed ratio of said speed changer ina direction to maintain said torque constant. y

A'further object ofv this invention isto provide a constant tension`drive comprising a power transmitting element mounted one. shaft forlimited angular movement thereon, with resilient means between saidpower transmitting element and the shaft, and means for changing thespeed of said drive upon relative movement ,o t said shaft and powertransmitting element against the iniluence of said resilient means.

A further object of this invention is to' provide a sheave mounted forlimited angular movement on a shaft, with spring means for biasing saidsheave in one direction, a switch carried by said shaft, and means forclosing said: switch upon predetermined angular movement of said sheaveon its shaft against the influence of saidspring.

A further object oi.' this invention is to provide means for adjustingthe spacing between said switch contacts, which maybe adjustable whilethe shaft is rotating.

A further object is to provide, in the mechanism recited above, aplurality of switches adapted to be closed at various relative angularpositions of said shaft and sheave.

Other objects will become apparent from the sheaves I9, 20 and belts21|.

following detailed description, taken ln conjunction with the drawingainwhich:

, Fig. 1 is a diagrammatic showing of a constant tension drive inaccordance with this invention; Fig. 2 is an e1evation,.` partly insection,4 of a shaft and sheave illustrating a detail of the drive; Fig.3 is a sectional view taken on line III- III of Fig. 2;

Fig. 4 is a view similar to Fig. 2, but illustrating a modification: ,IY

Fig. 5 is a sectional view taken on line VV of Fig. 4:

Figs. 6 and 7 are fragmental views illustrating details of circuitconnections of the modification shown in Figs. 4 and,5;

, shaft and sheave similar to Fig..2, but illustrating a modincation inwhich the spacing' between switch contacts is adjustable during rotationof the shaft;

Fig. 9 is a sectional view taken on line IX-IX of Fig. 8; n

Fig. 10 is a detail View, partly in section, taken on line X-X of Fig.8; and s Y Fig. 1l isa diagrammatic lview showing a modiiicationfof thedrive illustrated in Fig. 1

While the drive of this invention is applicable to winding rolls,unwindingrolls, or intermediate rolls, -it is shown in Fig. 1 as beingapplied to a winding roll i5, on which is wound the material to betensioned, which is-shown as a strip of brass or the like i6. Roll I5 isdriven from output shaft l1 of speed changer Il, as by means of Constantspeed motor 23, energized from a power source 24, is connectedto driveinput shaft 28 of speed changer i8 through sheave 21 on motor shaft 28,V-belts 29, and sheave 30 on shaft 2l.

Speed chansen I8 in this instance comprises input shaft 26 and outputshaft I'I connected by a plurality of V-belts 32 `connecting adjustablediameter sheaves and 3l.- ,These sheaves comthis' way, energizationv ofmotor 38 alters the speed ratio of the input' and output shafts 26, Ilof speed changer I8. Pilot motor 36 is energized from source 24 through'a switch 40 carried on sheave 30, the contacts of said switch being con.

nected to collector rings 38. 39 which are in contact with brushes 4I,42, respectively.

The details of the construction of speed changer I8 form no part of thepresent invention, and need notl be described herein. A-detaileddescription of the speed changer may be found in Patent No.2,221,l66issue'd to Casper W. Heinrich and Eugene J. Otto on November12, 1940. While this particular speed changer is described herein forpurposes of illustration, it is clear that any other known type of speedchanger may be substituted therefor.

` With motor 36 normally deenergized, constant speed motor 23 normallydrives winding roll I6 at a constant speed through speed changer I8.' Asthe strip I6 builds up on roll I5, its effective diameter increases, andthe material I6 is wound on roll I at afaster rate. This tends toincrease the tension on strip I6, and the work done by motor 23increases. Since the speed of the motoris substantially constant, theincreased work done by the motor is reflected in a higher motor torque.As described below, this increase in torque is utilized to energizepilot motor 36 to reduce the speed of output shaft I1, thereby reducingthe speed of rotation of roll I5. until equilibrium is reestablished.This reduction in the speed of roll I3 is repeated from time to time,until the winding step is completed.

Means for closing switch 40 in response to a change in torque on themotor drive is bestshown in Figs. 2 and 3. This torque-responsive switchmay be carried by either constant speed motor shaft 28 or constant speedinput shaft 26 of the speed changer. As. shown in Figs. 2 and 3, inputshaft 26 carries fixed thereon a sleeve 43 provided with spring'arm 44and switch arm 45. Spring arm 44 has a spring seat 41 near the endthereof, and also carries an adjustable stop screw 48 retained in anydesired position by lock nut 49.

Switch arm 45 carries a plunger 5I for actuating switch 48. Plunger 5Iis slidably retained in the bore of plunger housing 52, and is biased tothe right as seen in Fig. 2 by a spring 54 backed by plimger guide 53,the latter being retained by lock nut 63. Housing 52 is threaded in atapped bore in switch arm 45, and is retained by means of lock mit 55.

V-belt sheave 36 is freely mounted on sleeve 43 for limited angular'movement with respect to shaft 26. The sheave is provided with aninternal lug or abutment 51 which is provided with a spring seat 58which cooperates with spring seat 41 to support a helical compressionspring 59. A bolt 6I passes through sp'ring arm 44, helical spring 59,and lug 51, being suitably retained at both ends to provide for themaximum desired spacing between arm 44 and lug 51. The minimum spacingbetween arm 44 and lug 51 is determined by the settingv of stop screw 48which cooperates with lug 51 to prevent too great a degree of movementbetween shaft 26 and sheave 30 after switch 48 has been closed.

Inward of its outer flange, sheave 30 carries a lug or bracket 62 whichsupports insulated switch 46, which is normally open but may be closedby a slight pressure on switch button 63. Leads 64 and 65 electricallyconnect the switch contacts (not shown) with collector rings 38 and 89,respectively, which are suitably supported on and insulated from sleeve43. Brushes 4I and 42 connect with rings 38 and 38, respectively, toclose the circuit to pilot motor 36 through switch 40.

The normal position of sheave 30 on -shaft 26 is shown in Fig. 2. It isassumed that sheave 30 l drives shaft 26 in a clockwise direction, asseen in Fig. 2. When the torque on shaft 26 exceeds a predeterminedamount.sheave 38 moves clockwise with respect to shaft 26 against thepressure of spring 59. A predetermined degree of such relative movementresults in engagement between plunger 5I and switch button 63 to closeswitch 48. The amount of movement necessary rto actuate switch button 63may be determined by axial adjustment of plunger housing 52 in arm 45.As pointed outA above, the extent of relative angular movement betweensheave 36 and shaft 26 is limited by stop screw 48.

Closing of switch 48 energizes pilot motor- 36 t0 reduce the speed ofoutput shaft I1 of the speed changer, thereby reducing the speed of rollI5 and the tension on strip I6. This in turn reduces the torque onvshaft 26, whereupon sheave 36 resumes the normal position shown in Fig.2, opening switch 46 and deenergizing pilot motor 36. The drivecontinues at its reduced speed until the tension tends to increaseagain. This operation is repeated a number of times during the windingoperation, maintaining a substantially constant tension on strip I6.

While the construction ofFigs. 2 and 3 has been described with referenceto a winding roll, it will be understood that, by locating switch 40 onthe opposite side of switch operating arm 45, and modifying theconnections to pilot motor 36 to operate in the reverse direction uponclosing switch 40, constant tension on an unwinding roll may be providedby repeatedly speeding up output shaft I1 as the strip I6 unwinds fromroll I6.

One arrangement of this type is illustrated in Figs. 4-7, whichillustrate a construction which may be utilized ona winding roll, anunwinding roll, or an intermediate roll, to maintain sub-.

stantialiy constant tension thereon. As before, speed changer inputshaft 26 carries sheave 36, freely mounted for limited angular movementwith respect to the shaft. Sleeve 43 is fixedly mounted on shaft 26 andcarries spring arm 44 and switch actuating arm 45. :As in themodification of Fig. 2, compression spring 59 is mounted between sheavelug 51 and shaft arm 44, the maximum extension of the spring beingdetermined bythe setting of bolt 6I,` and the maximum compression of thespring being determined by the setting of stop screw 48.

In the modification of Fig. 4, however, two switches 48 and 48 areprovided, one on each side of switch arm 45. These switches aresupported on sheave 36 by means of brackets or lugs 62,62'.,respectively. In each case, the switch is operable by contact ofplunger 6I, 6I with switch button 63 or 63', plungers 5I, 5I' beingadjustably carried by arm 45 as previously de scribed. One contact fromeach switch is con. nected by leads 54, 64' with collector ring 38 (seeFig. 6); the other contact of switch 40 `is connected to collector ring39 by means of lead 65; while the remaining contact of switch 46' isconnected to collector ring 39' by means of lead 66' (see Fig. 7).Current is taken from collector rings 39', 38 and 39 by means of brushes42', 4I and 42, respectively, and connections are made from brushes 42',4I and 42 in such manner (not shown) that when switch 46 is closed thepilot -motor will be energized in one direction (to increase the speedof output shaft I1) when switch 46' is closed, the pilot motor will beenergized in the opposite direction (to decrease the speed 0f outputshaft I1): and when both switches are open. the pilot motor isdeenergized, and the speed ratio of speed changer I8 remains coniicationillustrated stent; Since such motor connections are well known and formno part oi' the present invention. they are not illustrated herein.

It will be understood that spring 59 is adjusted so' that, at 'apredetermined desired tension, i

switch operat g arm 45 will be maintained at the-neutral ition-shown in4,-pilot motor 36 being deenergized Ifl the tensiony increases,

erate with the, threaded portionot hollow actuating screw 19. theinnerend ot which .is iixediy supported in the-,inner race of friotionlessbearing 30, the outerfracesof which is iixedly mounted assuming shaft 2Bis driven by sheave 3U in a counterclockwise direction as seen in'.lFig. 4;.

sheave 3U' will move slightly in a counterclockwise -direction withArespect to shalt 26 ag'amst the pressure oi spring 59, until switch 40l'is closed. Thereupon pilot: motor 36 will be energized to operateinra.' direction to change the speed ratioof speed changer I6' to1reduce the .Nermany ,geen er and nandwneei 1t 'fare clutched togetherdue to the action. of springt n plunger 83.,..-.,Dl1rmg.=rctation ofshaft 26 and 'sheave 30. knob 82 and handwheel 16 and the tension onstripI I6. Should tension on strip `I6 become reduced beyond apredetermined point, sheave 30 would move a few degrees in a clockwisedirection with respect to shaft 26 under the iniiuence of spring 53. toclose switchil. This would energize'pilot motor 36 to operate in -adirection Vto change the speed ratio `oi!l speed changer i8 to increasethe tension on strip I6. Therefore the arrangement orV Figs.v 4-7 isa'pplicable to winding rolls-unwinding rolls or intermediate'rolls of astrip mill.

The above modifications of the invention provide a tension responsiveswitch which operates satisfactorily where a predetermined, I' constanttension is desired. The degree of tension required to actuate the switchmay be adiusted either by changing the' preset compression of spring 59or by axial movement of hollow screw 'or plunger casing 52=or 52', whichchanges the extent of relative angular.' movement of sheave 33 requiredto actuate switch 40 or 40'. But=in order-"to effectuate either 'ofthese changes', it is necessary to stop the drive. Sometimes it` isdesired to alter the tension of thestrip while the drive is inoperation.' For this purpose the modiin Figs. f8, 9 and 10 has beenprovided. if

In'thismo'diicationf, sheave 30 is mountedrfor *limited angular movementwith respectto shaft 26, as before, lwith compression spring 59 carriedbetween the sheave and shaft arm 44. Shaft arm 45 carries a slidableplunger case 61 which 4is biased to thev right (Fig. 8) by compressionspring 68. Plunger 5I is carried in plunger dasingfl, and is biased tothel left by spring-54, which is retainedmetween a iiange on plunger 5Iand plunger guide 53. The extending end of plunger 5I abutsza bell cranklever 69 which is urged toward plunger 5l by' spring 10. Switch button63 is located within spring 10 and is adapted to be actuated byunterclockwise movementof bell crank lever 69, Fig. 10. Plungei" carrier61 is slidably supported in a guide in arm 45 and is biased to the leftunder the action of spring 68, as seen in Fig. 8. The

by a cam 12. As shown in Fig. 10, cam 12 is inclined with respect to theaxis of plunger .case

61,-and movement of cam 12 axially of shaft 26 determines the initialaxial position of plunger case,61, thereby determining the extent ofrelative angular movement. between shaft 26l and sheave 30 required toactuate switch 40.

parts connected thereto may bes'stationary, ,or may rotate with theshaft and sheave.y If it be desired to ymove cam 512 to change thesetting of switch operating plunger casing 61, handwheel 16 maybegrasped with fine-band to hoidit stationary, while knob. 82 is pulledoutwardly out o! clutchingengagementfwith handwheel 16. Knob M i's thenturned angularly, this angularmqvement being transmitted to actuating"screw 13 'throughy splin'ed,v plunger 8 3.-- Actuating screw" 13 beingretained .against axial movement by frictionless-@thrust bearing-30Erotation of actuating screw; 19 results in axial mevement of handwheel13, the hub of which isfin threadedengagement ,with actuator.: screw 16.Axial movement of handwheel 16 is'transmitted to disk 13 through axialposition of plunger carrier 611s determined thrust Vbearing 15, therebycausingaxial movement of cam 12 which determines the position of plungercasing-61. It is clearirom the above description=. that the modicationLillustrated in Figs. 8, 9and l0 providesmeans for determining andchanging, while the `drive-is inl operation, the ..a 1nqunt of angularmovement ,between sheave 3B and shaft 26 required to close switch ou fli." l

While the-.description herein refers Vto a 1-belt sheave 3Q, it' Aisclearthat it would be within the Ascope of this invention to utilize 'ailat belt pulley, a, gear, or other mechanical powertransmitting elementon shaft 2mn lieu-:oi sheave 30', andthe word pulley as used in theclaims is intended to include such power transmitting elements.Furthermore, while the description relates to .the spring biased sheavebeingmounted onf-speed changer input shaft 26, it could-equally well bemounted on motor shaft 28 or any shaft intermediate these. Obviously,the -tispring biased sheave may be utilized-anywhere on the linput sideof the speed changer.

A further modiiled construction in accordance with this invention isillustratedt in il, wherein a motor 23, energized from power-source24drives winding ro1l,- |5 through a speed'iphanger i8. The latterisadapted to have its ratio between input s 1 1 26 and output shaft l1changed by lmeans of.; ilot motor 3,6, Pilot motor 36 is energized.bywnormally open switch 3l operable by gurrentre'sponsive relay 63,which caribe adjusted to oper'e' at any desiredigurrent by ineans ofadjustable heostat oii-othergimpedance 90. Il',y during the strip I6increases, the torque on motor 23 will increase and motor 23 will drawa'heavie'il current from line 24. Upon a predetermined increase ofcurrent to motor 23, current responsive relay 83 will close switch 88energizing pilot motor 36 tol reduce the speed of output shaft l1androll I5. When the speed of roll i5 has been reduced sur winding'operatiii tension` on ciently to restore the tension on strip I8 to adesired value, the torque on motor 23 will return to normal, the currenttaken by motor 23 will return to normal, relay 89 will open switch 88,and pilot motor I6 will be deenergized until the tension should againincrease.

While specific modifications of the invention have been illustrated anddescribed, it will be understood that modifications and equivalents suchas readily occur to those skilled in the art are included within thescope of this invention which is intended to be limited only by thescope of the claims appended hereto.

It is claimed and desired to secure by Letters Patent:

1. A constant tension drive for a winding roll, comprising a motor, aspeed changer provided with an input shaft and an output shaft. meansconnecting said motor to said input shaft com.- prising a pulley mountedfor limited rotary movement with respect to its shaft, resilient meansbiasing said pulley toward one angular position with respect to itsshaft, and means responsive to relative angular movement of said pulleyon its shaft against the pressure of said spring for changing the speedratio of said speed changer.

2. A constant tension drive for a winding roll, comprising a motor, aspeed changer provided with an input shaft and an output shaft, meansconnecting said motor in driving relationship with said input shaftcomprising a pulley mounted in driving relationship with its shaftthrough a spring, a pilot motor for decreasing the speed ratio betweensaid output and input shafts, a switch carried by said pulley forenergizing said pilot motor, and means for closing said switch uponpredetermined angular movement of said pulley with respect to its shaftagainst the iniiuence of said spring.

3. A drive as defined in claim 2, and means for adjusting the extent ofangular movement of said pulley on its shaft required to close saidswitch. f

4. In combination, a speed changer comprising interconnected input andoutput shafts, means for changing the specdratio of said shafts, amotor, means including a pulley connecting said motor to said inputshaft, said pulley :being spring biased for limited angular movement onits shaft,

and means responsive to angular movement of said pulley on its shaft foractuating said speed ratio changing means.

5. The combination as defined in claim 4, said speed ratio changingmeans comprising a pilot motor, a normally opened switch for energizingsaid pilot motor carried by said pulley, and means for closing saidswitch upon predetermined angular movement of said pulley on its shaft.

6. In combination, a speed changer comprising input and output shafts, adrive interconnecting said input and output shafts, means for changingthe speed ratio of said shafts, a motor connected to drive said inputshaft, the driving means between said motor and said drive` connectingthe input and output shafts comprising a pulley which is spring Vbiasedfor limited angular movement on its shaft, and means responsive toangular movement of said pulley and its shaft for actuating y prising aspring biased rotary power transmitting element mounted on a shaft forlimited angular motion relative to said shaft and serving to transmitpower from said source of rotary power to said speed changer, and meansresponsive to relative angular movement between said power transmittingelement and said shaft for changing the speed ratio of said speedchanger.

' 8. A variable speed ratio transmission comprising a rotary powertransmitting shaft, a rotary power transmitting element mounted forlimited angular movement relative to said shaft, resilient powertransmitting means between said element and said shaft, and means tovary the speed ratio of said transmission in response to relativeangular movement of said element and said shaft.

' EUGENE J.O'ITO.

